Czech Technical University in Prague Faculty of Civil Engineering

Department of Microenvironmental and Building Services Engineering

Czech Technical University in Prague Faculty of Civil Engineering

Department of Microenvironmental and Building Services Engineering

SE20 – Heating systemsSE20 – Heating systemsSE20 – Heating systemsSE20 – Heating systemsLecture 1Lecture 1

IntroductionIntroduction

Lecture 1Lecture 1

IntroductionIntroduction

Doc.Ing.Karel Kabele,CSc.Doc.Ing.Karel Kabele,CSc.

Room: Room: A122A122

kabelekabele@fsv.cvut.cz@fsv.cvut.cz

Lectures scheduleLectures schedule

11 The built environment. Applied thermo mechanics.The built environment. Applied thermo mechanics.22 MULCOMMULCOM33 Heat loss and consumption calculations. Principles of heating Heat loss and consumption calculations. Principles of heating

equipment. equipment. 44 Heat emittersHeat emitters, space heating, space heating55 (Easter Monday)(Easter Monday)66 Heating systemsHeating systems 77 Heating systemsHeating systems88 Boilers, boiler plantsBoilers, boiler plants99 Heat exchangers, district heatingHeat exchangers, district heating1010 Renewable sources, combined heat and power plantsRenewable sources, combined heat and power plants1111 Safety device for central heating systemsSafety device for central heating systems1212 Pumps in heating systemsPumps in heating systems13 13 Hot water generationHot water generation1414 Heating system control, building energy management systemsHeating system control, building energy management systems

History 700 B.C. - 0History 700 B.C. - 0

HypocaustaHypocaustaGreece, Italy, Greece, Italy,

TurkeyTurkey

Historie – medieval ageHistorie – medieval age

Stoves, fireplacesStoves, fireplaces

History 18-19.century History 18-19.century steamsteam

History 20.centuryHistory 20.centuryhot-water systemshot-water systems

Electricity,Water systemsCast-iron boilersCoal, Gas

Boiler Strebl 1927

Present and future?Present and future? Warm water Warm water

systemssystems Gas boilers Gas boilers

controled by controled by microprecessormicroprecessor

Heat emmitters Heat emmitters located in the floor, located in the floor, walls and ceilingwalls and ceiling

Computer modelling Computer modelling and simulationand simulation

Applied thermodynamicsApplied thermodynamics

Heat, heat energyHeat, heat energy Heat is the energy transferred between a Heat is the energy transferred between a

system and its surroundings due solely to a system and its surroundings due solely to a temperature difference between the system temperature difference between the system and some parts of its surroundings.and some parts of its surroundings.

TemperatureTemperature State variable describing kinetics energy of State variable describing kinetics energy of

the particles of the systemthe particles of the system Thermodynamic Thermodynamic /Kelvin/ /Kelvin/ T T [[KK]] Celsius t Celsius t [[°C°C]] t= T-273,15 t= T-273,15 Fahrenheit Fahrenheit [[°F°F]] 1°F=5/9°C 1°F=5/9°C (°F-32).5/9=°C(°F-32).5/9=°C

Basic laws of Basic laws of thermodynamicsthermodynamics

Zeroth law Zeroth law There is a state variable There is a state variable TEMPERATURETEMPERATURE. Two . Two

systems at the same temperature are in systems at the same temperature are in thermodynamics equilibrium. thermodynamics equilibrium.

The zeroth law of thermodynamics states that The zeroth law of thermodynamics states that if for example you have a Body (A) and a Body if for example you have a Body (A) and a Body (B), both at the same temperature; and then (B), both at the same temperature; and then you have a Body (C) which is at the same you have a Body (C) which is at the same temperature as Body (B); Therefore the temperature as Body (B); Therefore the temperature of Body (C) is equal to the temperature of Body (C) is equal to the temperature of Body (A). temperature of Body (A).

Basic laws of Basic laws of thermodynamicsthermodynamics

1.law1.law The total energy of the system plus the The total energy of the system plus the

surroundings is constant.surroundings is constant. 2.law2.law

The second law is concerned with The second law is concerned with entropy (S)entropy (S), , which is a which is a measure of disordermeasure of disorder. . The The entropy of the universe increasesentropy of the universe increases..

3.law3.law It is impossible to cool a body to absolute zero It is impossible to cool a body to absolute zero

by any finite processby any finite process

Heat transfer modesHeat transfer modes Heat ConductionHeat Conduction

Heat is transferred between two Heat is transferred between two systems through a connecting medium, systems through a connecting medium, Biot-FourierBiot-Fourier

Heat Convection Heat Convection Macroscopic movement of the matter in Macroscopic movement of the matter in

the forms of convection currents. the forms of convection currents. Newton-Richman, Fourier-KirchhofNewton-Richman, Fourier-Kirchhof

Heat transferHeat transfer

TransmissionTransmission convection+conduction+convectionconvection+conduction+convection

Radiation Radiation Electromagnetic wavesElectromagnetic waves

Indoor environmentIndoor environment Theory of the indoor environmentTheory of the indoor environment

Hygrothermal microclimateHygrothermal microclimate Acoustic Acoustic microclimatemicroclimate Psychical Psychical microclimatemicroclimate Light Light microclimatemicroclimate Electrostatic Electrostatic microclimatemicroclimate

Hygrothermal microclimateHygrothermal microclimate Indoor environment state from the viewpint of Indoor environment state from the viewpint of

thermal and moisture folws between the thermal and moisture folws between the human body and surroundingshuman body and surroundings

Heat Exchange between the Heat Exchange between the Human Body and the EnviromentHuman Body and the Enviroment

Metabolic Rate MMetabolic Rate M degree of muscular activities,degree of muscular activities, environmental conditions environmental conditions body size.body size.

Heat loss QHeat loss Q RespirationRespiration ConvectionConvection RadiationRadiation ConductionConduction EvaporationEvaporation

Body thermal balance equationBody thermal balance equationM=Q comfortM=Q comfortMM>Q >Q hothotMM<Q <Q coldcold

T

a

T

p

Factors Influencing Thermal Factors Influencing Thermal ComfortComfort

HumanHuman Metabolic RateMetabolic Rate Clothing InsulationClothing Insulation

SpaceSpace Air Temperature (Dry-Bulb)Air Temperature (Dry-Bulb) Relative HumidityRelative Humidity Air VelocityAir Velocity Radiation (Mean Radiant Temperature)Radiation (Mean Radiant Temperature)

Environmental indicesEnvironmental indices

Operative TemperatureOperative Temperature

where    where    ttgg = operative temperature = operative temperature                         ttaa = ambient air temperature = ambient air temperature                         ttrr = mean radiant temperature = mean radiant temperature                         hhcc = convective heat transfer coefficient = convective heat transfer coefficient                         hhrr = mean radiative heat transfer = mean radiative heat transfer coefficientcoefficient

rc

rrc

hh

thth a

gt

Environmental indicesEnvironmental indices Mean Radiant TemperatureMean Radiant Temperature

where    where    tr = mean radiant temperaturetr = mean radiant temperature Ti = temperature of the surrounding Ti = temperature of the surrounding

surface i, surface i, i=1,2,....,ni=1,2,....,n φφrnrn = shape factor which indicates the = shape factor which indicates the

fraction of total radiant energy leaving fraction of total radiant energy leaving the clothing surface 0 and arriving the clothing surface 0 and arriving directly on surface i, i=1,2,...ndirectly on surface i, i=1,2,...n

273.T....Tt 4 4nrn

41rr1r

MeasurinMeasuring g

instrumeinstrumentsnts

Thermal comfort Thermal comfort evaluationevaluation

PMV index PMV index (Predicted mean (Predicted mean vote)vote)

PPD index PPD index (Predicted (Predicted percentage of percentage of dissatisfied)dissatisfied)